The present invention relates generally to network appliances, and more particularly, to network appliances configured to measure or detect certain physical conditions and report such conditions to a remote monitoring device via a wired or wireless data network.
In recent years, businesses in most all industries have improved their productivity by linking their computer systems via a local area network and/or wide area network and installing software systems to track and manage the status of the business""s operations. This has enabled businesses to automate many tasks that were traditionally performed using manual paper based systems.
The network infrastructure employed in such systems typically includes a cabled backbone communicating data between various computing systems utilizing a protocol such as Ethernet. The physical topology of the cabled backbone complies with the chosen standard and typically will provide for the coupling of computing systems throughout most geographic areas of the facility. Each computing device typically includes a network interface card (NIC) which interfaces with the computer""s operating system software and includes hardware and firmware for transmitting and receiving data across the network backbone.
These types of networks have evolved to include other types of intelligent systems such as application specific network appliances.
While it has been contemplated that various application specific devices such as smoke detectors or security alarms could be coupled to a remote computer utilizing such a network, such devices have not heretofore been practical. Coupling such a device to the network backbone using existing technology would require a processor and network interface circuitry for encoding the data into an Ethernet compliant message, modulating the message onto a carrier signal, and transmitting to a remote computing device via the network. The cost and size associated with such an implementation could significantly increase the cost of the device. Further yet, as complex modulation schemes, frequency diverse redundant data schemes and other schemes used to improve data transmission rates and reduce bit error rates become more complicated, the circuitry required to interface with other devices on the network also becomes more complicated and thus expensive. Again, a full implementation of the network protocol in such devices is expensive and unnecessary.
Therefore, what is needed is an inexpensive network appliance with an electronic architecture which enables such an appliance to be coupled to a network and to report measured or detected conditions to a remote computer via such network without suffering the disadvantages of known technology.
A first object of this invention is to provide a network appliance transmitter comprising a memory storing transmission signal values representing a transmission frame of a predetermined message complying with a predetermined network protocol, and a transmitter coupled to the memory generating a modulated carrier signal representing the transmission frame. Preferably, the transmission signal values represent a network address of a remote computing device, a network address of the network appliance, a network protocol compliant preamble and message data. The memory may store transmission signal values representing a plurality of transmission frames, each transmission frame including distinct message data.
In one embodiment, the transmission signal values represent a modulated carrier signal and the transmitter includes a D/A converter receiving the transmission signal values and outputting the modulated carrier. The modulated carrier signal may be a quadrature amplitude modulated carrier signal.
In a second embodiment, the transmission signal values represent a base band transmission and the transmitter includes a mixer for mixing the base band transmission up to a carrier frequency and a D/A converter for generating the modulated carrier. Again, the modulated carrier signal may be a quadrature amplitude modulated carrier signal.
In a third embodiment, the transmission signal values represent a base band transmission and the transmitter includes a D/A converter generating an analog base band signal and an analog mixer for generating the modulated carrier. Yet again, the modulated carrier signal may be a quadrature amplitude modulated carrier signal.
A second objective of the present invention is to provide a network device for reporting one of a plurality of conditions to another network device across a data network, the device comprising: a) a detection circuit for detecting a condition and generating a condition signal representative of such condition; b) a memory storing transmission signal values representing a transmission frame of a predetermined message complying with a predetermined network protocol; and b) a transmitter coupled to the memory generating a modulated carrier signal representing the transmission frame. Preferably, the transmission signal values represents a network address of the remote computing device, a network address of the network appliance, a network protocol compliant preamble and message data. The memory may store transmission signal values representing a plurality of transmission frames, each transmission frame including distinct message data.
In one embodiment, the transmission signal values represent a modulated carrier signal and the transmitter includes a D/A converter receiving the transmission signal values and outputting the modulated carrier.
In a second embodiment, the transmission signal values represent a base band transmission and the transmitter includes a mixer for mixing the base band transmission up to a carrier frequency and a D/A converter for generating the modulated carrier.
In a third embodiment, the transmission signal values represent a base band transmission and the transmitter includes a D/A converter generating an analog base band signal and an analog mixer for generating the modulated carrier.
A third objective of the present invention is to provide a method of reporting a condition to a remote computing device, the method comprising: a) detecting the condition and generating a signal representative thereof; b) selecting a transmission frame corresponding to the condition from a plurality of transmission frames prestored in a memory; and c) transmitting the selected transmission frame on a network backbone. Preferably, the transmission frame is stored as a sequence of digital values representing a modulated carrier and transmitting the selected transmission frame includes clocking the sequence of values into a D/A converter to generate a modulated carrier signal.
Alternatively, the transmission frame may be stored as a sequence of digital values representing a base band signal and transmitting the selected transmission frame includes mixing the base band signal up to sequence of values representing a modulated carrier and clocking the sequence of values into a D/A converter to generate a modulated carrier signal.
Alternatively yet, the transmission frame may be stored as a sequence of digital values representing a base band signal and transmitting the selected transmission frame includes clocking the baseband signal into a D/A converter to generate an analog base band signal and mixing the analog base band signal with a carrier signal to generate a modulated carrier signal.